5-Fluorouracil (hereinafter sometimes referred to as “5-FU”), various derivatives thereof (such as tegafur, carmofur, doxifluridine, etc.), and like fluorouracil drugs are widely used as anticancer drugs at present. It is known that 5-FU administered to the body is first degraded by the action of dihydropyrimidine dehydrogenase (hereinafter sometimes referred to as “DPD”), which is the first enzyme in the pyrimidine metabolic pathway. It is therefore believed that the concomitant use of a drug that inhibits DPD enzymatic activity is effective in sustaining the effects of fluorouracil drugs such as 5-FU and the like. On the other hand, it is known that when a fluorouracil drug such as 5-FU is administered to a subject with DPD deficiency or reduced DPD activity, the drug is not metabolized in a normal manner and results in an abnormally high fluorouracil drug concentration in the blood, thereby causing severe side effects (e.g., myelosuppression, digestive symptoms, etc).
Thus, in order to effectively exhibit the action of fluorouracil drugs or prevent the side effects of fluorouracil drugs, diagnosis of pyrimidine-metabolic capacity, i.e., the existence, degree, etc., of a pyrimidine metabolic disorder in the subject, before administration of a fluorouracil drug is believed to be important.
A method for diagnosing pyrimidine metabolic activity in a subject has been reported in which an isotope-labeled pyrimidine compound is administered to the subject, and the excretion behavior of the isotope-labeled metabolic product discharged from the body is measured so as to determine the pyrimidine metabolic capacity, i.e., the existence, degree, etc., of a pyrimidine metabolic disorder in the subject (e.g., Patent Document 1). Granules and subtle granules containing isotope-labeled pyrimidine compounds and carriers are already known as pyrimidine metabolic capacity diagnosis preparations for use in the above method.
However, isotope-labeled pyrimidine compounds, such as 13C-uracil, have, as well as low solubility, characteristically high cohesiveness, although bulk powders of such compounds themselves are fine particles of several microns. Therefore, granules and subtle granules prepared from isotope-labeled pyrimidine compounds as such by standard methods do not rapidly dissolve, and partly because of this, the compounds have disadvantages such as a slow and non-uniform absorption rate in the living body and variation in the absorption rate due to individual differences. Therefore, in order to realize pyrimidine metabolic capacity diagnosis with higher accuracy, it is desired to overcome the above defects so that variation in the excretion time and amount of the isotope-labeled metabolic products can be reduced and the non-uniformity of diagnosis accuracy due to individual differences can be decreased.
Patent Document 1: International Publication No. WO 02/072153, pamphlet